Offshore construction and vessel

ABSTRACT

A construction jack-up barge comprising a barge (11) supporting a tower (13) in a stowed horizontal position for transport and a vertical position for deployment. The tower (13) has three fold-out legs (15), each equipped with a footing assembly (17). The tower (13) is supported for rotation between a horizontal stowed position and a vertical position for deployment, about the barge (11), by a pivotal connection (19). The tower is also supported in a traveling frame (20) which has concave shaped rollers (21) which track each chord of the tower (13), allowing the tower (13) to be moved up and down relative to the barge (11), when the tower is being deployed. In the vertical position the tower (13) is received through an opening which extends through the deck to the hull of the barge (11). A central cut out portion (33) extends from the stern of the barge (11), to the opening, to provide a pathway for the tower (13) as it rotates between the horizontal and vertical positions. The barge may be jacked up clear of the water, and may be separated from the column to enable the embarking therefrom.

FIELD OF THE INVENTION

This invention relates to the field of offshore constructions such asplatforms, which are located usually above sea level, supported from thesea bed from columns, towers or pylons.

BACKGROUND OF THE INVENTION

Typical offshore platforms comprise a plurality of towers supportedvertically in a barge, for towing to or self propelled navigation to theposition of deployment, whereupon the towers are lowered verticallyuntil they reach the sea bed. Subsequently the barge, which is to serveas a platform or the like, is jacked up the towers, clear of the surfaceof the sea.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention there is provideda jack-up construction comprising a column and a vessel, said columnbeing supportable on said vessel in a substantially horizontal positionfor storage or transport, and supportable in relation to said vessel ina substantially vertical position for deployment or use, wherein saidconstruction includes a support structure for supporting said column forrotation between said horizontal position and said vertical position,and wherein said support structure includes an element which selectivelyallows for said vessel and said column to be disconnected to enable saidvessel to embark from and dock to said column.

Preferably said support structure includes a pivotal connectionextending between said column and said vessel. In this manner, thepivotal connection provides for rotation of the column relative to thevessel.

Preferably said element comprises a pivoting portion on said carriagewhich in a closed condition secures said column for sliding movement,and restrains said column in said vertical position.

Alternatively said pivotal connection is dismountable from said columnand said carriage to enable said vessel and said column to bedisconnected. With such a configuration, it would be necessary to securesaid column against sliding, relative to said column, when said vesselis detached.

Preferably said jack-up construction includes hoisting means to movesaid column vertically, relative to said vessel, when said column is insaid vertical position.

In accordance with a second aspect of the invention there is provided avessel adapted for deployment as an offshore structure supported abovethe sea floor, said vessel including a support structure for supportinga column for rotation between a substantially horizontal stowed positionand a vertical position for deployment, said support structure includingan element allowing for said vessel and said column to be connected toenable said vessel to dock to said column, and disconnected to enablesaid vessel to embark from said column.

Preferably said support structure includes a pivotal connection pointfor forming a pivotal connection between said column and said vessel.

Preferably said support structure includes a carriage for supportingsaid column for selective sliding movement in relation thereto. In thismanner, the column slides relative to the carriage as the vessel isjacked up or down the column.

Preferably said carriage includes flanged wheels or concave shapedpulleys for guiding said column.

Preferably said pivotal connection extends between said carriage andsaid vessel.

Preferably said carriage is dismountable from said column to enable saidvessel and said column to be disconnected.

Preferably said carriage includes guide means for guiding verticaldisplacement of said vessel relative to said column.

Preferably said element comprises a pivoting portion on said carriagewhich in a closed condition secures said column for sliding movement,and restrains said column in said vertical position.

Alternatively said pivotal connection is adapted to be selectivelyconnectable to connect/disconnect said vessel and said column.

Preferably said vessel includes hoisting means for moving said columnvertically relative to said vessel, when said vessel is attached to saidcolumn and when said column is in said vertical position.

Preferably said vessel includes an opening extending vertically throughthe hull and deck of said vessel, through which said column is receivedin said vertical position.

Preferably said opening includes a recess along the edge of said vessel.

Preferably said opening is located away from the edge of said vessel,and said recess provides access from the edge of said vessel to saidopening.

Preferably said opening is located at a relative central position insaid vessel.

Preferably said recess extends to the stern of said vessel.

Preferably said vessel includes cover means for covering said recesswhen access thereto is not required.

Preferably said cover means comprises removable cover portions.

Preferably said vessel includes floodable compartments to allowbalancing of the weight distribution of said vessel, relative to saidcolumn.

Preferably said vessel supports cranes for loading and unloadingequipment. The cranes may be pedestal mounted or gantry mounted cranesas required.

In accordance with a third aspect of the invention there is provided acolumn for supporting a vessel and adapted for deployment as an offshorestructure supported above the sea floor, said column having a supportstructure for selectively attaching to said vessel to allow said vesselto dock to or embark from said column, said support structure includinga pivotal connection point for forming a pivotal connection between saidcolumn and said vessel when said column and said vessel are attached toallow said column to be rotated relative to said vessel from ahorizontal stowed position to a vertical position for deployment.

Preferably said supporting means includes a carriage adapted to traversesaid column, and which may be fixed to said column as required.

Preferably said column is adapted to be hoisted vertically up or downrelative to said vessel when said pivotal connection is disconnected.

Preferably said column includes a weight distribution structure at thelowermost end thereof.

Preferably said weight distribution structure comprises at least threefold out legs.

Preferably each of said fold out legs includes a footing.

Preferably said footing includes a floodable chamber.

Preferably said footing comprises a sealable enclosure formed by anupper cup and a lower cup arranged one inside the other in telescopingalignment and defining a pressurable chamber therein, said pressurablechamber having inlet/outlet means for transfer of fluid in or out ofsaid chamber.

Preferably said footing includes an axial guide assembly for alignmentof the cups relative to each other.

Preferably said axial guide assembly includes a pair of members arrangedto telescope along an axis co-parallel with the axial extent of saidfooting.

Preferably said cups are cylindrical.

Preferably said axis is coincident with the axial extent of saidfooting.

Preferably said members are tubular.

Preferably said members include a locking device to secure said membersrelative to each other.

Preferably said locking device comprises a wedge driveable into anannular collar located at the junction of said members.

Preferably said wedge is slidable along the inner member of saidtelescoping member and comprises a frustum bored along the axis thereof.

Alternatively, said locking device comprises a grout injection systemadapted to in ject a settable grout composition to lock said members.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in the following description of onespecific embodiment thereof, in which:

FIG. 1 is a side view of an offshore construction jack-up barge having acolumn shown in the stowed condition;

FIG. 2 is a side view of the construction jack-up barge showing theweight distribution structure of the column being deployed;

FIG. 3 is a side view of the construction jack-up barge showing thecolumn being deployed;

FIG. 4 is a side view of the construction jack-up barge showing thecolumn deployed in an in field transit configuration;

FIG. 5 is a side view of the construction jack-up barge with the columnin the horizontal (stowed) position, showing the pivotal connectionbetween the barge and the column;

FIG. 6 is a side view of the construction jack-up barge with the columnin the vertical position, also showing the pivotal connection betweenthe barge and column;

FIG. 7 is a plan view of guide means for the column in the verticalposition;

FIGS. 8 and 9 are side views showing hoisting means for moving the bargeand column relative to each other;

FIG. 10 is a perspective view of the barge;

FIG. 11 is a side view of the construction jack-up barge shown in apre-load configuration;

FIG. 11a is a plan schematic showing the ballast configuration of thebarge for pre-load configuration;

FIG. 12 is a side view of the construction jack-up barge shown preparinga permanent offshore platform installation;

FIG. 13 is a side view of the completed permanent offshore platforminstallation;

FIG. 14 is a side view of the construction jack-up barge showing stage 1of a typical installation sequence;

FIG. 14a is a plan view of the ballast configuration of the constructionjack-up barge for stage 1 of the installation sequence shown in FIG. 14;

FIG. 15 is a side view of the construction jack-up barge showing stage 2of the installation sequence;

FIG. 16 is a side view of the construction jack-up barge showing stage 3of the installation sequence;

FIG. 17 is a side view of the construction jack-up barge showing stage 4of the installation sequence;

FIG. 18 is a side view of the construction jack-up barge showing stage 5of the installation sequence;

FIG. 19 is a side view of the construction jack-up barge showing stage 6of the installation sequence shown in FIG. 14;

FIG. 20 is a side view of the construction jack-up barge showing thedismantling thereof after completion of the installation sequence shownin FIGS. 14 to 19;

FIG. 21 is a side view of the construction jack-up barge equipped with ahaul winch for hauling materials along the seabed;

FIG. 22 is a view of detail of a footing assembly;

FIG. 22a is a cut away view of detail of part of the footing assemblyshown in FIG. 22;

FIG. 22b is a cut away view of detail of the axial guide for the footingassembly shown in FIG. 22; and

FIG. 22c is a cut away view of detail of the footing assembly shown inFIG. 22.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment is directed towards a construction jack-up barge assemblyfor transporting and erecting an offshore tower for supporting aplatform or the like.

The construction jack-up barge comprises a vessel in the form of a barge11 supporting a column in the form of a large chord square section tower13. The tower 13 has a weight distribution structure in the form ofthree fold out legs 15, each equipped with a footing assembly 17. Thelegs 15 are folded along the tower 13, in a retracted position, in whichthe tower assembly may be transported on the barge 11, as shown inFIG. 1. Referring to FIG. 5, the tower 13 is supported for rotationbetween a horizontal stowed position and a vertical position fordeployment, about the barge 11, by a pivotal connection 19. The pivotalconnection 19 is achieved by a pin and clevis arrangement secured to acarriage in the form of a travelling frame 20 which has concave shapedrollers 21 which track each chord of the tower 13. The carriage andpivotal connection 19 form a support structure for the tower 13. Theconstruction jack-up barge may conveniently include suitable means forsecuring the tower 13 in the horizontal stowed position, to preventdamage in transit, in the event of rough seas or swell.

The tower 13 is pivotable from the horizontal position as shown in FIG.5 to a vertical position as shown in FIG. 6, the vertical positioncorresponding to the deployed condition. The tower 13 is guided in thevertical position by two guide assemblies 22 and the travelling frame20, which allow for sliding vertical movement of the tower 13 therein.Each guide assembly 22 has removable end portions 23 which are lockedinto place after the tower has been received within the guide assembly22. The guide assemblies 22 and moveable end portions 23 are preferablylined with a bearing surface such as ultra-high molecular weightpolyethylene (uhmw). Movement of the removable end portions 23 isaccomplished by two hydraulic rams 24, one connected to each end portion23. The guide assemblies 22 are provided at the top of the cabinsuperstructure 25 of the barge 11, and in the hull below the waterlineof the barge 11. The guide assemblies 22 may be considered as definingan opening which extends vertically from the bottom of the hull throughto the deck of the barge, for receiving the tower in the verticalposition. Referring now to FIG. 10, the guide assemblies 22 andclevis-like parts 27 of the pivotal connection 19 may be seen, in theperspective view of the barge 11.

The barge 11 includes a pair of gantry type cranes 29, each mounted on atrack 31 for movement fore and aft, along the side of the barge 11.Removable cantilever beams 32 are provided at the stern of the barge 11in order to permit outboard travel of the gantry cranes 29, to providegreater access for hoisting loads and reduce the turning moment exertedon the crane when doing so.

The barge 11 also includes a central cut out portion 33 extending fromthe stern of the barge 11, to the opening through which the tower 13extends in the vertical position. The central cut out portion 33 extendsvertically through the hull and deck of said vessel, and provides apathway for transit of the tower 13 between the horizontal and thevertical positions.

Referring now to FIGS. 1-4, the construction jack-up barge includesenough stowage space on the deck, alongside the tower 13, for storage offurther tower sections 35, which are provided to be fitted to the top ofthe tower 13, once it has been deployed in the vertical position, andthe barge 11 has been jacked up the tower 13.

Deployment of the tower 13 to the vertical position begins with thefolding out of the legs 15 to the outward position as shown in FIG. 2,at which they are secured. The cranes 29 are utilized at this stage toassist with laying back of the legs 15 and the footing assemblies 17.The lowermost leg 15a and its footing 17 passes through the central cutout portion 33.

The cranes 29 are then used to assist in rotating the tower 13 from thehorizontal stowed position shown in FIG. 1, through the position shownin FIG. 3, until the tower 13 reaches the vertical position shown inFIG. 4.

Hoisting of the tower 13 relative to the barge, either upwards ordownwards is provided for by a pair of 4.5 meter tension type jacks 37which connect to the travelling frame 20 which may be pinned to thetower cords through apertures 41 located therein. The jacks 37 are shownin the retracted position in FIG. 8, and the extended position in FIG.9. In order to lower the tower 13 relative to the barge 11, and pull thebarge up the tower, once the footings 17 reach the seabed, the pivotalconnection 19 is broken, and then the frame 20 is secured to the tower13 as shown in FIG. 9, and the jacks 37 are retracted to the positionshown in FIG. 8. The tower 13 and barge 11 are pinned together, whilethe frame 20 is detached from the tower 13, and moved to the extendedposition as shown in FIG. 9, before being secured again for repeating ofthe step.

In order to raise the tower 13 relative to the barge, (i.e. lower thebarge 11 on the tower 13) the same operation is performed, but inreverse.

Referring now to FIG. 7, once the tower 13 reaches the verticalposition, the end portions 23 of the guide assembly 22 are fitted inplace, to lock the tower 13 in the vertical position. The jacks 37 arethen fitted and the pivotal connection 19 is broken, and the tower 13may be jacked down until the footing assemblies 17 reach the seabed.Alternatively, if it is desired to set the offshore installation up inshallow water, the tower 13, with its legs extended, may be raised to ashigh a position as possible, as shown in FIG. 4, to provide minimumdraft while the barge 11 and tower 13 are manoeuvred to the final sitefor the offshore installation.

To assist with settling the footing assemblies 17 in the seabed, whilstminimizing their weight for transport, the footings are of hollowconstruction and floodable with seawater, in order to reduce theirbuoyancy. Conversely, to assist in dislocating the footing assemblies 17from the seabed, if it is desired to dismantle the offshoreinstallation, an air pump and valve assembly is provided for eachfooting assemblies 17 so that the footing assemblies 17 may be filledwith air to displace the water, and to increase the buoyancy of thefooting assemblies 17 as the tower 13 is raised relative to the barge11.

Referring now to FIG. 11, once the footing assemblies 17 have reachedthe seabed 45, the barge 11 is jacked up the tower 13, clear of thesurface 47 of the sea. The barge 11 has three separate sea water ballasttanks 49, which are filled to increase the downward bearing weight onthe tower structure 13, and settle the footing assemblies 17 in theseabed. The seawater ballast tanks 49 may be filled appropriately tocounterbalance any uneven loading on the barge 11. It will be understoodthat the number of ballast tanks incorporated into the barge may bevaried as required. The footing assemblies 17 also include heightadjustment means, to counteract the effects of the seabed 45 beinguneven or there being uneven settling of the footing assemblies 17 intothe seabed 45.

Referring to FIGS. 12 and 13, steps in the construction of a permanentoffshore installation incorporating a heli-deck 51 and living andworking space 53, are shown. The crane 29 is shown in FIG. 12positioning tower sections 35 atop the tower 13 until the desired heightis reached, whereupon the heli-deck 51 and other structures areinstalled. A material barge 55 is shown in FIG. 12, and is utilised inorder to bring additional materials to the construction site asrequired.

Once the offshore installation has been completed, the barge 11 may belowered down to the sea surface, and disengaged and manoeuvred away fromthe tower 13. In FIG. 13, a floating boat landing 57 which extendsaround the tower 13, is shown. The boat landing 57 is fitted once thebarge 11 has left. Hoists on the super structure of the installation maybe utilized to hoist the boat landing clear of wave action, when it isnot in use, or when there are large seas or swell. The footingassemblies 17 are shown with foundation piles 59 providing securing ofthe offshore installation to the seabed 45.

FIGS. 14 to 19 show steps in building an offshore installation 61 usingthe construction jack-up barge and tower assembly. FIG. 14a shows theseawater ballast tanks 49 which are employed in such applications.Hoisting of a primary substructure 63 is achieved by a pair of strandjacks 65 mounted on a beam across the central cut out portion 33 of thebarge 11. Referring to FIG. 20, once the offshore installation 61 iscomplete, the installation tower formed by the construction jack-upbarge 11 and its tower 13 are dismantled and returned to the stowedcondition, as shown in FIG. 1.

Referring to FIG. 21, the construction jack-up barge assembly is shownin a hoisting configuration, for hoisting undersea pipelines or cablesor the like. A rotary drum hoist 71 is fitted to beams extending acrossthe central cut out portion 43 of the barge 11, and exerts tractiveforce on a cable 73 which extends downward to a pulley 75 located belowthe surface 47 of the sea, the cable 73 then extending outward, to whereit is joined onto pipelines or cables which are being pulled out towardthe construction jack-up barge.

Referring now to FIG. 22, details of the most preferred footing assemblyare shown. Each footing assembly 17 comprises a sealable enclosureformed by an upper cup 76 and a lower cup 77. The upper and lower cups76 and 77 are of cylindrical form, with the lower cup 77 being ofsmaller diameter than the upper cup 76. The lower cup 77 is arranged fortelescoping movement within the upper cup 76 and may be pressurised orhave the volume of water or air within the enclosure formed by the cupsvaried, to provide a travel of nominally 1.5 meters vertically inrelation to the upper cup, providing planar and settlement adjustmentfor the tower structure. The lower cup 77 is shown in the extendedposition in dashed outline, indicated at 79.

The cups are nominally 5.5 meters in diameter and approximately 2.9meters in depth.

A pair of circular bearing pads 80 and 80a attached to the lower cup 77and upper cup 76 respectively, provide bearing surfaces for relativemovement of the cups. The sealable enclosure is maintained sealed fromthe outside environment by a packer 81 formed of rubber or a compositesynthetic material. Alternatively, the packer may be an inflatable typewhich may receive fluid under pressure to prevent leakage therepast fromthe sealable enclosure, to permit pressurisation of the sealableenclosure with either air or water. If required, further packers may beprovided to give some redundancy, ensuring that the event of leakagepast one packer will not cause failure of the footing.

The top and bottom of the cups are formed as a flattened cone with thetower outrigger structure/legs 15 tied directly into the upper cup 76.

An axial guide assembly is incorporated along the sealable enclosure/cupcentreline, and comprises a pair of tubular members 82 and 83 attachedto the lower cup 77 and upper cup 76 respectively.

A telescopic mechanical locking device consisting of a bearing collar 84and an hydraulically operated wedge collar 85 is incorporated on thetubular members 82 and 83, to fix the cup travel after adjustment. Thetelescopic mechanical locking device may be-replaced by a grout plug,which is achieved by a conduit extending down the tubular member 83, toinject a settable grout composition, to secure the tubular membersrelative to each other. The grout plug arrangement would be utilized inmore permanent installations which on decommissioning would requireejection of the set grout plug under hydraulic pressure, and disassemblyof the sealable enclosure to remove the plug before the footing could berestored to a servicable condition.

The sealable enclosure includes valves to seal the interior thereof, thevalves being connected to piping to selectively allow for flooding,venting, air blow down, and suction, and a pressure relief system toensure that the footing is not overstressed. Water is used forpressurization for level adjustment. The footing assembly may bedeballasted for additional buoyancy, using air blowdown.

While the footing described is particularly advantageous, alternateseabed support configuration options include conventional mud mats withhydraulic rams, fixed mud mat and pile sleeve combinations for permanentpiled installation and a rectangular footing with a plan area similar tothat of the jack-up barge.

Apart from the seawater ballast tanks 49, below the cabin superstructure25, there is provided one level of accommodation including a workshop,stores, a galley and mess, and a lounge, including space for storage offood, water, and waste. In the cabin superstructure, there is providedaccommodation for 28 workers, in addition to the ablutions and otherspace as may be required. The central cut out portion 33 has removabledecking, which may be put into place when construction work has beencompleted. This is particularly useful, if the barge 11 is to be used asaccommodation space atop a tower in an offshore installation.

The construction jack-up barge according to the invention offersadvantages over existing known equipment. It may be convenientlydeployed in shallow water, and relatively deep water although, it isprimarily intended for application in waters having a depth range from 4to 40 meters, assuming a tidal range of 3 m. The barge in the embodimenthas a length of 27 meters and a beam of 20 meters, with a loaded draftranging from 4 to 9 meters.

The principle of using a single tower allows floating access beneath thebarge which allows loads to be positioned closer to a crane located onthe barge. This decreases the turning moment placed on any crane,especially where the crane pedestal is located near the edge of the deckof the barge, due to the configuration of a single tower allowing heavyloads to be lifted closer to the pedestal of the crane.

The single tower with the three leg or outrigger distribution structureat the base also permits better distribution of loads onto the seabed.

Furthermore, and importantly, the method of stowage of the tower,whereby the tower is laid out in a substantially horizontal position,reduces the height of the overall assembly above the water line, andallows access of the jack-up barge assembly to areas on water, where dueto height restrictions, traditional jack-up barges would not be able toreach.

The erected tower may support more than one jack-up barge if this isrequired. This enables a further barge containing process equipment orthe like to be deployed on the same erected tower.

It should be appreciated that the scope of the invention is not limitedto the embodiment described herein, whereby the invention may be appliedto jack-up barges having more than one column or tower.

I claim:
 1. A vessel adapted for deployment as an offshore structuresupported above the sea floor, said vessel including a support structurefor supporting a column for rotation between a substantially horizontalstowed position and a vertical position for deployment, wherein saidsupport structure includes a carriage for supporting said column forselective sliding movement in relation thereto while said column is insaid vertical position wherein said vessel includes an element allowingfor said vessel and said column to be connected to enable said vessel todock to said column in said vertical position, and disconnected toenable said vessel to embark from said column in said vertical position,and wherein said vessel includes guide means for guiding slidingmovement of said column in relation thereto while said column is in saidvertical position.
 2. A vessel as claimed in claim 1 wherein saidsupport structure includes a pivotal connection point for forming apivotal connection between said column and said vessel.
 3. A vessel asclaimed in claim 2 wherein said pivotal connection extends between saidcarriage and said vessel.
 4. A vessel as claimed in claim 3 wherein saidpivotal connection is selectively connectable to enable said vessel todock to and embark from said column in said vertical position.
 5. Avessel as claimed in claim 1 wherein said carriage includes concaveshaped pulleys for guiding said column.
 6. A vessel as claimed in claim1 wherein said element comprises a pivoting portion on said vessel whichin a closed condition secures said column for sliding movement, andrestrains said column in said vertical position.
 7. A vessel as claimedin claim 1 wherein said vessel includes hoisting means for moving saidcolumn vertically relative to said vessel, when said vessel is attachedto said column and when said column is in said vertical position.
 8. Avessel as claimed in claim 1 including an opening located near thecenter of said vessel and extending vertically through the hull and deckof said vessel, through which said column is received in said verticalposition, said opening extending to an edge of the vessel to accommodatesaid column as said column is rotated between said vertical position andsaid substantially horizontal stowed position.
 9. A vessel as claimed inclaim 1 wherein said vessel includes floodable compartments to allowbalancing of the weight distribution of said vessel, relative to saidcolumn.
 10. A column for supporting said vessel and adapted fordeployment as an offshore structure supported above the sea floor, saidcolumn having a support structure for selectively attaching to saidvessel to allow said vessel to dock to and embark from said column,wherein said support structure includes a pivotal connection point forforming a pivotal connection between said column and said vessel whensaid column and said vessel are attached to allow said column to berotated relative to said vessel from a horizontal stowed position to avertical position for deployment and wherein said support structureincludes a carriage adapted to traverse said column, and which may befixed to said column to allow said column to be hoisted up and downrelative to said vessel.
 11. A column as claimed in claim 10 includingmeans for hoisting vertically up and down relative to said vessel whensaid pivotal connection is disconnected, to allow said column to behoisted up and down relative to said vessel.
 12. A column as claimed inclaim 10 including a weight distribution structure comprising at leastthree fold-out legs at the lowermost end thereof.
 13. A column asclaimed in claim 12 wherein each of said fold out legs includes afooting.
 14. A column as claimed in claim 13 wherein each said footingcomprises a sealable enclosure formed by a cylindrical upper cup and acylindrical lower cup arranged one inside the other in telescopingalignment and defining a pressurable and floodable chamber therein. 15.A column as claimed in claim 14 wherein said footing includes an axialguide assembly for alignment of the cups relative to each other.
 16. Acolumn as claimed in claim 15 wherein said axial guide assembly includesa pair of members arranged to telescope along an axis co-parallel withthe axial extent of said footing.
 17. A column as claimed in claim 16wherein said members include a locking device comprising a wedgedriveable into an annular collar located at the junction of saidmembers.
 18. A column as claimed in claim 17 wherein said wedge isslidable along the inner member of said telescoping member and comprisesa frustum bored along the axis thereof.
 19. A jack-up constructioncomprising a vessel, and column for supporting said vessel and adaptedfor deployment as an offshore structure supported above the sea floor,said column having a support structure for selectively attaching to saidvessel to allow said vessel to dock to and embark from said column,wherein said support structure includes a pivotal connection point forforming a pivotal connection between said column and said vessel whensaid column and said vessel are attached to allow said column to berotated relative to said vessel from a horizontal stowed position to avertical position for deployment and wherein said support structureincludes a carriage adapted to traverse said column, and which may befixed to said column to allow said column to be hoisted up and downrelative to said vessel, said vessel including an element allowing forsaid vessel and said column to be connected to enable said vessel todock to said column, and disconnected to enable said vessel to embarkfrom said column.
 20. A jack-up construction as claimed in claim 19wherein said carriage includes concave shaped pulleys for guiding saidcolumn.
 21. A jack-up construction as claimed in claim 19 wherein saidpivotal connection extends between said carriage and said vessel.
 22. Ajack-up construction as claimed in claim 19 wherein said elementcomprises a pivoting portion on said carriage which in a closedcondition secures said column for sliding movement, and restrains saidcolumn in said vertical position.
 23. A jack-up construction as claimedin claim 19 including an opening located near the center of said vesseland extending vertically through the hull and deck of said vessel,through which said column is received in said vertical position, saidopening extending to an edge of the vessel to accommodate said column assaid column is rotated between said vertical position and saidsubstantially horizontal stowed position.
 24. A jack-up construction asclaimed in claim 19 wherein said vessel includes hoisting means formoving said column vertically relative to said vessel, when said vesselis attached to said column and when said column is in said verticalposition.
 25. A jack-up construction as claimed in claim 19 wherein saidvessel includes floodable compartments to allow balancing of the weightdistribution of said vessel, relative to said column.